The present invention relates generally to power generation systems, and more particularly, to methods and apparatus for preheating feedwater in power generation systems.
At least some known conventional fossil fuel burning power generation systems include a steam cycle power-producing turbine system. Steam turbines are used in known power plants, such as Integrated Gasification Combined Cycle (IGCC) power plants, Natural Gas Combined Cycle (NGCC) power plants, and coal-fired steam cycle power plants. In at least some known power plants, only about 40% of the heat energy contained in the fossil fuel is converted to electricity by a generator. This leaves a large portion of the heat energy wasted in the water cooling towers or other water cooling facilities. At least some known water cooling facilities transfer all of the waste heat in the low pressure exhaust steam to the environment through the vaporization of cooling water.
Additionally, at least some known power plants include a carbon dioxide capture system for separating carbon dioxide from flue gases. Such capture systems may require a large amount of energy provided in the form of steam from the power plant. The extraction of steam from the steam turbine reduces the electricity generation and, thus, the overall efficiency of the power plant. At least some known carbon dioxide capture systems include processes, such as desulphurization, solvent regeneration, and compression, requiring cooling towers that waste a large portion of the heat energy during cooling.